Electrode material additive, preparation method thereof and battery

Abstract

The invention relates to an electrode material additive, a preparation method thereof and a battery, the electrode material additive comprises an end chain and a polymeric chain link containing a silicon-oxygen bond, the end chain is connected with the end part of the polymeric chain link, and the end chain comprises a polar chain segment; the polymerized chain link is rotationally polymerized into a core body, and an end chain forms a shell to coat the core body. The electrode material additive can solve the problems of cracking, powder falling and falling caused by insufficient toughness of a pole piece.

Description

Technical Field

[0001] The present application relates to the technical field of electrode materials, and in particular to an electrode material additive, a preparation method thereof, and a battery. Background Art

[0002] With the rapid development of the global new energy industry, the attention to battery energy density is also increasing. In order to improve the battery energy density, the development of electrode material additives provides a good direction for progress. Electrode material additives can not only improve the slurry solid content and slurry processability during the slurry manufacturing process, but also reduce the use of NMP and reduce the energy consumption cost of coating and drying, which brings good news to improve the battery energy density.

[0003] However, the development of electrode material additives still cannot strip away the “copy and paste” of polymers in traditional dispersants. Although the introduction of polymer materials can reduce the viscosity of the slurry, as a rigid or brittle material, it is more likely to cause cracking of the pole piece, especially when thickly coated. Due to insufficient toughness and flexibility, the pole piece may crack, leak, or peel off when wound or folded, affecting the stability and durability of the coating, and further affecting the safety and life of the battery. Therefore, how to provide an electrode material additive that can improve the flexibility of the pole piece has become the key. Summary of the invention

[0004] The purpose of the present application is to provide an electrode material additive, a preparation method thereof and a battery, wherein the electrode material additive can solve the problem of cracking caused by insufficient toughness of the electrode piece.

[0005] To achieve the purpose of this application, this application provides the following technical solutions:

[0006] In a first aspect, the present invention provides an electrode material additive, comprising an end chain and a polymer chain segment containing a silicon-oxygen bond, wherein the end chain is connected to the end of the polymer chain segment, and the end chain comprises a polar segment; the polymer chain segment is swirled into a core body, and the end chain forms an outer shell to cover the core body.

[0007] In one embodiment, the molecular formula of the terminal chain and the polymeric chain segment containing silicon-oxygen bonds comprises R q -(C2H6SiO) n SiC2H6-R q , where R q For the terminal chain, (C2H6SiO) n is the polymer chain segment.

[0008] In one embodiment, R q Including R α (R β ) p R γ , where Rα Including anchoring groups, R β Including polar segments, R γ It comprises a connecting group segment, wherein the connecting group segment connects the polar segment and the polymer segment, wherein 2≤p≤20.

[0009] In one embodiment, the anchoring group includes at least one of an ether bond, a carbonyl group, an ester group, an amide group, a hydroxyl group, a carboxylic acid group, a phosphate group, a phenol, an amine group, a benzene ring, a sulfonic acid group, a phosphate ester group, and a hydrazine; and / or

[0010] The polar segment includes at least one of a polyester segment, a polyether segment, and a polyacrylate segment.

[0011] In one embodiment, the weight average molecular weight of the end chain and the polymer chain segment containing silicon-oxygen bonds is 700 to 3500; and / or

[0012] The degree of polymerization of the polymerized chain segment is 4 to 30; and / or

[0013] The molecular weight dispersity of the terminal chain and the polymer chain segment containing silicon-oxygen bonds is 1.2-3.

[0014] In one embodiment, the electrode material additive further includes an adhesion additive, and the adhesion additive includes at least one of polyacrylonitrile, polyvinyl alcohol, polyacrylic acid, polyvinylidene chloride, polyimide, polyamide, and polyethyleneimine.

[0015] In a second aspect, the present invention provides a method for preparing an electrode material additive, comprising:

[0016] The first precursor and the second precursor are mixed and reacted according to a mass ratio to obtain an electrode material additive;

[0017] Among them, the first precursor contains a polymer chain segment containing a silicon-oxygen bond, and the second precursor contains an end chain, and the end chain includes a polar segment; the end chain is connected to the end of the polymer chain segment, the polymer chain segment is rotated into a core body, and the end chain forms an outer shell to cover the core body.

[0018] In one embodiment, the first precursor and the second precursor are mixed and reacted according to a mass ratio, comprising:

[0019] The first precursor and the first auxiliary agent are mixed and reacted according to a mass ratio to obtain a first solution;

[0020] The second precursor and the second auxiliary agent are added to the first solution according to a mass ratio for mixed reaction to obtain the electrode material additive.

[0021] In a third aspect, the present invention provides a battery comprising an electrolyte, a separator and a pole piece, wherein the pole piece comprises a current collector and an active material layer arranged on the current collector, wherein the active material layer is formed by coating an active slurry, and the active slurry comprises an electrode material additive as described in any one of the various embodiments in the first aspect or an electrode material additive prepared by the preparation method as described in any one of the various embodiments in the second aspect.

[0022] In one embodiment, the electrode material additive accounts for 0.05% to 0.3% by mass of the active slurry; and / or

[0023] The limiting surface density of the pole piece is 25 mg / cm 2 ~75mg / cm 2 ; and / or

[0024] The surface density of the pole piece is 18±1 mg / cm 2 When the softness value of the electrode is 550mN to 950mN; and / or

[0025] The surface density of the pole piece is 18±1 mg / cm 2 And the compacted density is 2.65±0.35mg / cm 3 When the pole piece is folded in half for 4 or more times; and / or

[0026] When the active slurry is coated and dried and the shell and the core are disintegrated, the dissociation extension of the polymer chain segment is 5% to 10%; and / or

[0027] The peeling force of the pole piece is 0.5N / cm to 0.7N / cm; and / or,

[0028] The surface density and compaction density of the pole piece are 18±1 mg / cm 2 and 2.65±0.35mg / cm 3 When the pole piece has an elongation of ≤1.0%.

[0029] The electrode material additive provided in the present application includes a softening aid having both polar segments and polymer chain links, and the softening aid has a polymer chain link with a silicon-oxygen bond as a core, a polar segment as an outer shell, and the ends and end chains of the polymer chain link are connected by chemical bonds. The polymer chain link has a silicon-oxygen bond. Since the silicon-oxygen bond has a large bond angle and a small internal rotation steric hindrance, it has good flexibility even in a low temperature environment. The polar segment as the outer shell of the softening aid can improve the compatibility of the polymer chain link that is insoluble in the solvent or has poor compatibility with the solvent in the solvent through the wrapping of the polar outer shell. The core-shell structured softening aid can be affinity adsorbed with the active material through the polar outer shell in the battery slurry system to improve the stability of the interface structure. The polar outer shell also helps to improve the dispersion performance of the battery slurry and increase the solid content of the slurry to a certain extent. During the slurry coating and drying process, as the solvent evaporates, concentrated stress is generated locally on the surface of the electrode due to uneven heat dissipation and uneven surface tension distribution. At this time, the core-shell structure disintegrates and releases the core with polymerized chain links to stretch into a chain structure with efficient energy dissipation characteristics, thereby greatly improving the flexibility of the electrode and solving the problem of cracking, powdering and falling off caused by insufficient toughness of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 is a schematic diagram of a first component of an embodiment;

[0032] Figure 2 is a schematic diagram of a first component of another embodiment;

[0033] Figure 3 is a schematic structural diagram of a first component in one embodiment;

[0034] Figure 4 is a schematic structural diagram of a first component in another embodiment;

[0035] Figure 5 is a schematic structural diagram of a first component in yet another embodiment;

[0036] Figure 6 is a schematic structural diagram of the first component in another embodiment;

[0037] Figure 7 is a flow chart of the preparation of an electrode material additive in one embodiment;

[0038] Figure 8 is a flow chart of some steps for preparing an electrode material additive in one embodiment;

[0039] Fig. 9 is a graph showing the results of the folding flexibility test of the pole pieces of Example 1 and Comparative Example 3;

[0040] Fig.10 It is a graph showing the results of electrode coating of Example 1 and Comparative Example 3.

[0041] Description of reference numerals:

[0042] 100-first component, 10-shell, 20-core. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more of the related listed items.

[0045] It should be noted that the "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] All steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b, etc.

[0047] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0048] The electrode material additive of the present application can be added to the electrode material, and the electrode material includes a positive electrode material or a negative electrode material. In a specific embodiment, the electrode material additive can be added to the slurry of the electrode material of the aqueous system or the organic solvent system. The function of the electrode material additive is to increase the flexibility of the electrode piece made of the electrode material, improve the curling effect of the electrode piece, and prevent the electrode piece from cracking.

[0049] This application provides an electrode material additive, please refer to Figure 1 and Figure 3 .

[0050] The present invention provides an electrode material additive, including a first component 100, the first component 100 includes an end chain and a polymer chain segment containing a silicon-oxygen bond, the end chain is connected to the end of the polymer chain segment, and the end chain includes an anchoring group and / or a polar segment; the polymer chain segment is spun into a core body 20, and the end chain forms a shell 10 to cover the core body 20. Optionally, at least one end of the polymer chain segment is connected to the polar segment, and the number of polar segments can be one or more, without limitation. Optionally, the end chain forming the shell 10 can be any one of a polar segment, an anchoring group plus a polar segment. Specifically, the polar segment is connected to the polymer chain segment through an anchoring group.

[0051] like Figure 3 As shown, the repeatable unit corresponding to the bracket is a polymer chain link, R1 and R2 can be the same or different, without limitation. R1 and R2 can be polar groups or non-polar groups, without limitation. Optionally, R1 and R2 can be hydroxyl groups, silicon oxygen bonds, benzene rings, carboxylic acid groups, ketone groups, aldehyde groups, etc., without limitation. R3 and R4 are end chains.

[0052] Optional, such as Figure 4 As shown, the polymer chain segments are hyperbranched polymers, the hollow circles are oxygen atoms, the solid circles are silicon atoms, and the curves are polar groups or non-polar groups. Optionally, the non-polar groups can be alkanes (methane, ethane, propane, etc.), aromatic hydrocarbons (the benzene ring part in benzene and its derivatives), halogenated hydrocarbons (groups formed after halogen atoms replace hydrogen atoms on saturated carbon atoms, such as -CF3, -CCl3, etc.), and the polar groups can be acidic groups (carboxylic acid groups, phenolic groups), carbonyl groups (ketone groups, aldehyde groups), thiol groups, amino groups, halogen groups, etc.

[0053] The weight average molecular weight of the polymeric chain segment may be 500 to 2500. Optionally, the weight average molecular weight of the polymeric chain segment may be 500, 1000, 1500, 2000, or 2500.

[0054] In a specific embodiment, the polymer chain includes a polydimethylsiloxane segment as an example, and the molecular formula of the polydimethylsiloxane segment is -[Si(CH3)2O] n -, wherein the repeating unit is [Si(CH3)2O]. It should be explained that the present application does not limit the specific type of polymer chain segments, and organic substances including silicon-oxygen bonds can be used as polymer chain segments in the present application.

[0055] Optionally, the ends of the polymer chain segments may be provided with connecting groups to facilitate connection with the polar segments. The connecting groups may be provided at one or both ends of the polymer chain segments. The connecting groups may be at least one of succinic anhydride groups, Si-H groups, carboxyl groups, etc. Figure 5 As shown, the linking group is a succinic anhydride group and is disposed on both sides of the polymer chain segment, and R5 and R6 can be polar groups or non-polar groups without limitation. Figure 6 As shown, the linking group is a Si-H group. Figure 5 The polar segments in the corresponding to the amino-modified low molecular weight polyether, Figure 6 The polar segment in corresponds to poly(ethylene glycol) methacrylate.

[0056] The electrode material additive provided in the present application includes a first component 100 having both polar segments and polymer segments as a softening aid, and the polymer segments having silicon-oxygen bonds in the first component 100 serve as a core 20, and the polar segments and / or anchoring groups serve as a shell 10. The ends and end chains of the polymer segments are connected by chemical bonds. The polymer segments have silicon-oxygen bonds. Since the silicon-oxygen bonds have large bond angles and small internal rotation steric hindrance, they have good flexibility even in low temperature environments. The polar segments as the shell 10 of the first component 100 can improve the compatibility of polymer segments that are insoluble in solvents or have poor compatibility with solvents in the solvent through the wrapping of the polar shell 10. The first component 100 with a core-shell structure can be affinity-adsorbed with the active material through the polar shell 10 in the battery slurry system to improve the stability of the interface structure. The polar shell 10 also helps to improve the dispersion performance of the battery slurry and increase the solid content of the slurry to a certain extent. During the slurry coating and drying process, as the solvent evaporates, concentrated stress is generated locally on the surface of the electrode due to uneven heat dissipation and uneven surface tension distribution. At this time, the core-shell structure disintegrates and releases the core 20 with polymerized chain links to stretch into a chain structure with efficient energy dissipation characteristics, thereby greatly improving the flexibility of the electrode and solving the problem of cracking, powdering and falling off caused by insufficient toughness of the electrode.

[0057] For reference Figure 2 and Figure 4 In one embodiment, the first component 100 includes a plurality of end chains and a plurality of polymer segments, the plurality of end chains form a shell 10 , and the plurality of polymer segments form a core 20 .

[0058] Optionally, the core 20 may include some end chains, and the proportion of polar segments in the core 20 is less than the proportion of polymer segments. Specifically, the proportion of polar segments may not exceed 50%, 40%, 30%, 20%, 10%, etc., without limitation. The shell 10 may include some polymer segments, and the proportion of polymer segments in the shell 10 is less than the proportion of end chains. Specifically, the proportion of polymer segments may not exceed 50%, 40%, 30%, 20%, 10%, etc., without limitation. The inclusion of some polymer segments in the shell 10 helps to improve the flexibility of the pole piece even when the first component 100 has not yet disintegrated.

[0059] Optionally, the first component 100 is in the shape of a ball of wool, and is composed of a large number of polymer chain segments and end chains. The polymer chain segments and end chains are first stacked layer by layer and then folded and assembled to form a ball-like structure, thereby forming a core-shell structure.

[0060] Optionally, the first component 100 includes a hyperbranched polymer, and the terminal chains are connected to the branches of the hyperbranched polymer.

[0061] Optionally, the first component 100 is a spherical shape formed by a network polymer, and part of the branched chains of the network polymer are broken to form the shell 10 .

[0062] In one embodiment, the end chain further comprises an anchoring group, and the anchoring group comprises at least one of an ether bond, a carbonyl group, an ester group, an amide group, a hydroxyl group, a carboxylic acid group, a phosphoric acid group, a phenol, an amine group, a benzene ring, a sulfonic acid group, a phosphoric acid ester group, and a hydrazine. And / or, the polar segment comprises at least one of a polyester segment, a polyether segment, a polyacrylate segment, and a polyether segment.

[0063] Optionally, the end chain including the anchoring group and the polar segment may be one of polyetheramine, modified polyethylene glycol (NH2-PEG-X, X is an anchoring group), polypropylene glycol (NH2-PPG-X, X is an anchoring group), polyethylene glycol-block-polypropylene glycol (block is an anchoring group), polyethylene glycol-block-polytetrahydrofuran (block is an anchoring group), polyethylene glycol-block-polycaprolactone (block is an anchoring group), phenol polyoxyethylene ether, polyoxyethylene ether phosphate, modified polytetrahydrofuran (X1-PTMG-X2, X1 is a reactive group and X2 is an anchoring group), polyethylene glycol diacrylate (PEGDA), polyethylene glycol methyl methyl ether acrylate (PEGMA), polyacrylate, etc.

[0064] In one embodiment, the molecular formula of the terminal chain and the polymeric chain segment containing silicon oxygen bond comprises R q -(C2H6SiO) n SiC2H6-R q , where R q For the terminal chain, (C2H6SiO) n For polymer chain links.

[0065] Optional, R q are end chains connected to the ends of the polymer chain. q The molecular formulas of can be the same or different, without limitation. The end chain can be any one of a polar segment and an anchoring group plus a polar segment. Specifically, the polar segment is connected to the polymer segment through an anchoring group.

[0066] Optionally, the polymer chain segment may be a siloxane segment, specifically, the polymer chain segment may be one or more of a polydimethylsiloxane segment, a cyclopolydimethylsiloxane segment, a silicone segment, a halogenated siloxane segment, a carboxyl long-chain alkylsiloxane segment, a polyamidosiloxane segment, etc., wherein the number of repeating units containing silicon-oxygen bonds may be 4 to 30.

[0067] Specifically, the polymer chain segment includes polydimethylsiloxane, wherein n is the degree of polymerization of the polymer chain segment, and 4≤n≤30. The chemical formula of the polymer chain segment includes (C2H6SiO) n , refers to (C2H6SiO) n It can be a complete chemical formula of the polymer chain, that is, the polymer chain consists of carbon atoms, hydrogen atoms, oxygen atoms and silicon atoms. Of course, in other embodiments, the complete chemical formula of the polymer chain includes (C2H6SiO) n Segments or elements other than (C2H6SiO) n The repeating structure and partial element composition of the polymer chain segment are only indicated for adaptability. The polymer chain segment can also be double-end-modified, such as succinic anhydride double-end-modified, Si-H double-end-modified. Among them, other groups, such as benzene ring, ethyl, halogenated hydrocarbon, etc., can be connected to some silicon atoms of the polymer chain segment without limitation.

[0068] It should be noted that the molecular formula of the first component 100 contains R q -(C2H6SiO) n SiC2H6-R q , refers to the q -(C2H6SiO) n SiC2H6-R q It can be the complete molecular formula of the first component 100, that is, the first component 100 is composed of carbon atoms, hydrogen atoms, oxygen atoms, silicon atoms and terminal chains. Of course, in other embodiments, the complete chemical formula of the first component 100 includes the following: q -(C2H6SiO) n SiC2H6-R q Segments or elements other than R q -(C2H6SiO) n SiC2H6-R q The partial structure and partial element composition of the first component 100 are only indicated for adaptability. q -(C2H6SiO) n SiC2H6-R q Other side chains or elements may also be included. For example, the chemical formula of the first component 100 may also include sulfur atoms and phosphorus atoms. The number of either sulfur atoms or phosphorus atoms may be 0 or a non-negative number.

[0069] The present application provides a polymer chain segment containing silicon-oxygen bonds so that the first component 100 has good flexibility even at low temperatures, and then provides an end chain at at least one end of the polymer chain segment containing silicon-oxygen bonds, so that the end chain wraps the polymer chain segment and thus improves the compatibility of the polymer chain segment containing silicon-oxygen bonds in the solvent, and facilitates affinity adsorption with the active material in the battery slurry system. After the active slurry is dried, the shell 10 formed by the end chain decomposes, so that the first component 100 dissociates and unfolds in a chain shape, thereby achieving improvement in the flexibility of the electrode.

[0070] In one embodiment, R q Including R α (R β ) p R γ , where R q Including anchoring groups, R β Including polar segments, R γ It includes a connecting group segment, which connects the polar segment and the polymer segment, wherein 2≤p≤20.

[0071] Optionally, the anchoring group may include any one of an amine group, an amide group, an ether bond, a hydroxyl group, a carboxylic acid group, a phenol, a benzene ring, a phosphate group, a sulfonic acid group, and a hydrazine, and the end chain may also include other branches or elements. For example, the chemical formula of the end chain may also include C a1 H b1 O c1 N d1 S e1 P f1 , where S is a sulfur atom, P is a phosphorus atom, and any one of e1 and f1 can be 0 or a non-negative number. Specifically, when the terminal chain has a sulfur atom, the terminal chain can include a sulfonic acid group, and when the terminal chain has a phosphorus atom, the terminal chain can include a phosphate group. The anchoring group can also be an alkane chain containing 0 to 3 carbon atoms.

[0072] Optionally, the polar segment may be at least one of a polyether segment (including polyethylene glycol, polypropylene glycol, polytetrahydrofuran), a polyester segment (including polycaprolactone, polybutylene terephthalate), and a polyacrylate segment (including polybutyl acrylate, polyethyl acrylate, polyoctyl acrylate), without limitation.

[0073] Optionally, the linking group segment may include an alkane linking segment containing 1 to 5 carbon atoms, or an amide-containing linking segment, without limitation.

[0074] Optional, for reference Figure 5 The end chain contains polyether and amine group. Specifically, the polyether in the end chain serves as a polar segment, the amine group serves as an anchoring group, and the amine group is connected to the polymer chain segment. Figure 6 , poly(ethylene glycol) methacrylate serves as a polar segment in the terminal chain.

[0075] Specifically, the polyether in the end chain serves as a polar segment, the amine group serves as an anchoring group, and the amine group is connected to the polymer chain segment. The anchoring group is arranged in the polar segment to connect to the polymer chain segment, which helps to enhance the adhesion between the polar segment and the polymer chain segment, improve the stability of the polar segment and the polymer chain segment, and prevent the end chain and the polymer chain segment from falling off or decomposing.

[0076] The main repeating unit of the polymer chain segment of the present application is polydimethylsiloxane, so that the polymer chain segment has good flexibility, and the end chain contains nitrogen elements to make the end chain polar, so that the shell 10 formed by the end chain has polarity, thereby improving the compatibility of the first component 100 in the solution and facilitating adsorption with the active material.

[0077] In one embodiment, the weight average molecular weight of the terminal chains and the polymeric chain segments containing silicon-oxygen bonds, i.e., the weight average molecular weight of the first component 100, is 700 to 3500; and / or, the weight ratio of the polymeric chain segments to the polar segments is 1:0.2 to 0.5; and / or, the degree of polymerization of the polymeric chain segments is 4 to 30; and / or, the molecular weight of the terminal chains and the polymeric chain segments containing silicon-oxygen bonds, i.e., the molecular weight dispersity of the first component 100, is 1.2 to 3.

[0078] Optionally, the weight ratio of the polymer chain link to the polar segment is 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc., without limitation. The core-shell structure formed by the polymer chain link and the polar segment that meet this weight ratio has good structural stability. If the weight ratio of the polymer chain link to the polar segment in the polar segment is too low, the shell 10 composed of some polar segments may not be able to completely wrap the core body 20, resulting in part of the core body 20 being exposed to the outside, thereby affecting the overall performance and stability of the core-shell structure, resulting in an incomplete synthesized core-shell structure; if the weight ratio of the polymer chain link to the polar segment in the polar segment is too large, due to the poor compatibility of the polar segment and the polymer chain link, a stable core-shell structure cannot be formed. When the mass of the polar segment as the shell 10 accounts for a large proportion, it may cause the synthesized core-shell structure to separate the core body 20 from the shell 10 or form an independent phase. Phase separation phenomenon.

[0079] Optionally, the weight average molecular weight of the first component 100 may be 700, 1000, 1500, 2000, 2500, 3000, 3500, etc., without limitation. If the weight average molecular weight of the first component 100 is too low, the first component 100 will not be able to provide sufficient flexibility for the electrode, causing the electrode to be easily broken or deformed when subjected to external force, affecting the mechanical strength and durability of the battery, and reducing the service life of the battery. The first component 100 with too low molecular weight has poor solubility in the solvent, resulting in the inability to be evenly dispersed in the electrode material, which may cause instability or decline in battery performance. If the weight average molecular weight of the first component 100 is too high, the viscosity of the first component 100 will be too high, and the fluidity during electrode coating will be poor, making it difficult to coat evenly, etc., and the first component 100 with too high molecular weight may hinder the conduction of electrons in the electrode material, resulting in a decrease in the conductivity of the battery, thereby affecting the charge and discharge performance and energy density of the battery, and reducing the efficiency of the battery. The first component 100 meeting the weight average molecular weight range has suitable flexibility, dispersibility and bonding strength, good fluidity during electrode coating, and is easy to coat.

[0080] Optionally, the degree of polymerization of the polymer chain segment may be 4, 10, 15, 20, 25, 30, etc., without limitation. If the degree of polymerization of the polymer chain segment is too low, the molecular chain of the polymer chain segment will be shorter, resulting in poor intrinsic flexibility. In addition, the first component 100 will be easily soluble in the solvent and unable to swirl. If the degree of polymerization of the polymer chain segment is too high, it will have a serious negative impact on the peeling force and cohesion of the pole piece, affect the quality of the pole piece, and have a great impact on the cycle stability and safety performance of the battery. In addition, if the degree of polymerization is too large, the particles of the first component 100 as a softener will be too large, which will affect the uniform dispersion of the active material in the solvent, affect the compaction density of the pole piece, and easily lead to unstable pole piece quality, affecting the electrochemical performance. The flexibility of the polymer chain segment that meets this degree of polymerization range is good, which is conducive to the uniform dispersion of the active material in the solvent.

[0081] Optionally, the molecular weight dispersity of the first component 100 may be 1.2, 1.5, 1.8, 2, 2.5, 2.8, 3, etc., without limitation. If the molecular weight polydispersity of the first component 100 is too high, the first component 100 may exhibit uneven fluidity during processing, resulting in processing difficulties. Since the low molecular weight part is easy to become a stress concentration point, the first component 100 is more likely to break when subjected to force, which may also lead to a decrease in the mechanical properties of the first component 100, such as tensile strength and elastic modulus. When the molecular weight polydispersity of the first component 100 is too low, that is, when the molecular weight distribution is narrow, the solubility of the first component 100 in the solvent may deteriorate, and the compatibility with other materials may also be affected. The first component 100 that meets this molecular weight dispersity range has good mechanical properties and processing stability, and good solubility in the solvent.

[0082] In one embodiment, the electrode material additive further comprises an adhesion additive, wherein the adhesion additive serves as a second component.

[0083] Using an adhesion additive as the second component helps to enhance the bonding force between battery materials (such as positive and negative electrode materials, electrolytes, etc.), so that the battery materials are not easy to fall off or delaminate during the battery charging and discharging process; by improving the adhesion between materials, the second component can also improve the peeling strength of the pole piece, so that the pole piece is not easy to be peeled off when subjected to external force, which helps to extend the service life of the battery and reduce the risk of battery failure caused by pole piece shedding; the second component as an adhesion additive can also help disperse the particles in the battery material so that it is more evenly distributed in the electrolyte or other substrates, and improve the stability of the slurry by improving the dispersibility of the battery material, and prevent the particles from agglomerating or precipitating during storage and use. And the mixing of the first component 100 with the adhesion promoter can improve the disadvantage of poor adhesion to the substrate caused by the long silicon chain, so that the flexibility of the pole piece is greatly improved without deteriorating the performance of the pole piece and the battery.

[0084] In one embodiment, the mass ratio of the first component 100 to the second component is 100:(3.1-8.7); and / or the weight average molecular weight of the second component is 10,000-500,000; and / or the second component includes at least one of polyacrylonitrile, polyvinyl alcohol, polyacrylic acid, polyvinylidene chloride, polyimide, polyamide, and polyethyleneimine.

[0085] Optionally, the mass ratio of the first component 100 to the second component can be 100:3.1, 100:4, 100:5, 100:6, 100:7, 100:8, 100:8.7, etc., without limitation. When the mass ratio of the first component 100 to the second component is too large, the proportion of the first component 100 as a softener is too high, which may cause the hardness, strength and wear resistance of the electrode material to decrease, thereby affecting the stability and durability of the electrode during use. When the mass ratio of the first component 100 to the second component is too small, the proportion of the second component as an adhesion additive is too high, which may change the original distribution and arrangement of the electrode material, resulting in uneven porosity or excessive bonding points, thereby affecting the overall stability and cycle performance of the electrode. The first component 100 and the second component that meet this mass ratio range can not only achieve the effect of softening and enhancing the adhesion between the electrode material and the current collector or other coatings, but also will not affect the stability and cycle performance of the electrode.

[0086] Optionally, the weight average molecular weight of the second component may be 10000, 50000, 100000, 150000, 250000, 300000, 350000, 400000, 450000, 500000, etc., without limitation. The second component meeting the weight average molecular weight range has appropriate wettability and bonding strength, and good compatibility with the electrolyte, reducing the impact on the ion conductivity and electrochemical performance of the battery.

[0087] The present invention provides a method for preparing an electrode material additive. Figure 7 .

[0088] In one embodiment, the preparation method of the electrode material additive specifically comprises the following steps:

[0089] Step S10, mixing the first precursor and the second precursor according to a mass ratio to obtain an electrode material additive.

[0090] The first precursor comprises a polymer chain segment containing a silicon-oxygen bond, and the second precursor comprises an end chain, which includes an anchoring group and / or a polar segment; the end chain is connected to the end of the polymer chain segment, the polymer chain segment rotates into a core body, and the end chain forms an outer shell to cover the core body.

[0091] Specifically, the first precursor is in the form of microspheres or chains, without limitation.

[0092] Optionally, the ratio of the amount of the active functional group of the first precursor to the amount of the reactive functional group of the second precursor is 1:(1.1-1.5) to ensure that the active functional group of the first precursor reacts completely.

[0093] For reference Figure 8 In one implementation, step S10 includes:

[0094] Step S11, mixing the first precursor and the first auxiliary agent according to a mass ratio to obtain a first solution.

[0095] Step S12, adding the second precursor and the second auxiliary agent into the first solution according to the mass ratio for mixing and reaction to obtain an electrode material additive.

[0096] Specifically, in step S11, the first precursor may include a siloxane segment, and in step S11, a polymer segment containing a silicon-oxygen bond and a first auxiliary agent are added to deionized water, and the first auxiliary agent includes an emulsifier. The polymer segment may be polydimethylsiloxane and modified polydimethylsiloxane, such as succinic anhydride double-terminated modified polydimethylsiloxane and Si-H double-terminated modified polydimethylsiloxane.

[0097] In a specific embodiment, step S11 includes: mixing polydimethylsiloxane, an emulsifier, and deionized water in a mass ratio, stirring and heating the mixture under a protective airflow environment, and adding a pH adjuster to adjust the pH of the solution to obtain modified polydimethylsiloxane to form stable O / W (oil-in-water) emulsion microspheres.

[0098] Optionally, in step S11, the mass ratio of polydimethylsiloxane, emulsifier, and deionized water is 1:(0.02-0.1):(1.5-4). Optionally, the mass ratio of polydimethylsiloxane, emulsifier, and deionized water can be 1:0.02:1.5, 1:0.05:2, 1:0.08:3, 1:0.1:4.

[0099] Optionally, in step S11, the protective gas flow may include one of nitrogen and argon, and the stirring and heating reaction conditions are: placing the mixture in a water bath or oil bath and stirring at a speed of 600rpm to 1000rpm, the stirring time is 30min to 120min, and the reaction temperature is 50℃ to 70℃.

[0100] Optionally, in step S11, the hydrophile-lipophile balance value HLB of the emulsifier is ≥8, and the first auxiliary agent includes but is not limited to one of polycetearyl glucoside oxyethylene sorbitan monostearate, propylene glycol, steareth-21, oleth-10, PEG-100 stearate, sucrose stearate, sodium cetearyl sulfate, and sodium stearoyl glutamate.

[0101] Optionally, in step S11, a pH adjuster is added to adjust the pH of the solution to 8.0-10.0, and the pH adjuster includes but is not limited to one of disodium hydrogen phosphate, sodium bicarbonate, ammonia water, diethanolamine, and triethanolamine.

[0102] In a specific embodiment, the second auxiliary agent in step S12 includes a catalyst, and the catalyst can be one of pyridine, 4-dimethylaminopyridine (DMAP), and a platinum nanocatalyst. In a specific embodiment, the catalyst used when the double-terminated polydimethylsiloxane reacts with the second precursor using succinic anhydride is pyridine or DMAP, and the catalyst used when the double-terminated polydimethylsiloxane reacts with the second precursor using Si-H is a platinum nanocatalyst.

[0103] Optional, for reference Figure 8 , step S10 further includes:

[0104] Step S13, adding a demulsifier according to a mass ratio into the solution containing the first component to disperse and demulsify.

[0105] Step S14, performing a filtering.

[0106] Step S15, washing with pure water and ethanol for multiple times, filtering, and drying to obtain a solid first component.

[0107] Optionally, the mass ratio of the first component to the demulsifier may be 1:(0.1-0.2), the demulsifier includes but is not limited to one of calcium chloride, magnesium chloride, ferrous sulfate, and aluminum sulfate, and the dispersion and demulsification time may be 0.5h.

[0108] Optionally, in step S15, the drying process may be performed by performing reduced pressure evaporation at 60°C to 80°C for 6h to 10h.

[0109] In a specific embodiment, after the drying in step S15 is completed, a core-shell structured flexible and crack-proof additive having polydimethylsiloxane as a core layer and polar segments as a shell layer is obtained.

[0110] In one embodiment, the method further includes step S20: mixing and dispersing the first component, the second component, and the first solvent according to a weight ratio.

[0111] Specifically, the first solvent includes one of N-methylpyrrolidone (NMP), diacetyl, dimethyl sulfoxide, and methanol. Specifically, the weight ratio of the first component, the second component, and the first solvent is 47.5:2.5:50.

[0112] The present invention provides an electrode sheet, comprising a current collector and an active material layer arranged on the current collector, wherein the active material layer is formed by coating an active slurry, and the active slurry comprises an electrode material additive as described in any of the various embodiments described above or prepared by the aforementioned preparation method.

[0113] In one embodiment, the electrode sheet may be a positive electrode sheet or a negative electrode sheet, and both the positive electrode sheet and the negative electrode sheet may include the electrode material additives provided above. The active material layer includes a positive electrode material or a negative electrode material. Among them, the positive electrode material can reversibly deintercalate active lithium ions, and the active lithium ions migrate between the positive electrode and the negative electrode of the battery to realize battery charging and discharging. The positive electrode material may be a phosphate positive electrode material and a ternary positive electrode material. Exemplarily, the positive electrode material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate oxygen, lithium fluorinated vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. And a lithium supplement material may be added to the positive electrode material. Exemplarily, the lithium supplement material may be lithium iron-rich lithium, lithium cobalt-rich lithium, lithium nickel-rich lithium, etc.

[0114] Adding the electrode material additive of the present invention to the active slurry of the pole piece is beneficial to improving the thick coating crack prevention and flexibility of the pole piece.

[0115] In one embodiment, the mass ratio of the electrode material additive to the active slurry is 0.05% to 0.3%; and / or the limiting surface density of the electrode piece is 25 mg / cm2 ~75mg / cm 2 ; and / or, the surface density of the pole piece is 18±1mg / cm 2 When the softness value of the pole piece is 550mN~950mN; and / or the surface density of the pole piece is 18±1mg / cm 2 And the compacted density is 2.65±0.35mg / cm 3 When the pole piece is folded for more than 4 times (when the pole piece is coated on both sides, the surface density of each side is about 18mg / cm 2 , compacted density is about 2.65mg / cm 3 ) and / or, when the active slurry is coated and dried and the first group of decomposition bodies are formed, the dissociation extension of the polymer chain is 5% to 10%; and / or, the peeling force of the pole piece is 0.5N / cm to 0.7N / cm; and / or, the surface density of the pole piece is about 18mg / cm 2 And the compacted density is about 2.65mg / cm 3 When the elongation of the pole piece is ≤1.0%.

[0116] Optionally, the mass ratio of the electrode material additive to the active slurry can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc., without limitation. When the mass ratio of the electrode material additive to the active slurry is too large, the content of the active substance will be reduced, thereby affecting the capacity of the battery, and too much electrode material additive may also affect the pore structure of the electrode, which is not conducive to the penetration of the electrolyte and the transmission of ions. If the mass ratio of the electrode material additive to the active slurry is too small, the performance of the electrode material may not be fully exerted, resulting in a decrease in the utilization rate of the active substance, which in turn affects the capacity and energy density of the battery, and if the amount of the electrode material additive added is too small, it will affect the uniformity of the active slurry, resulting in uneven distribution of the active substance on the electrode, thereby affecting the performance and consistency of the electrode. The uniformity of the active slurry and the amount of active substance that meet the mass ratio of the electrode material additive to the active slurry are appropriate, the fluidity is good during electrode coating, it is easy to coat, and the battery capacity and energy density are large.

[0117] Optionally, the pole piece's limiting surface density can be 25 mg / cm 2 、35mg / cm 2 , 45mg / cm 2 、55mg / cm 2 、65mg / cm 2 、75mg / cm 2Etc., without restriction. When the limiting surface density of the pole piece is too small, the utilization rate of the active material of the battery during the charge and discharge process is reduced, thereby accelerating the degradation of the battery, and the insufficient surface density of the pole piece may also cause the pole piece to undergo structural changes during the cycle, such as expansion and contraction, further affecting the cycle stability of the battery. When the limiting surface density of the pole piece is too large, the porosity of the pole piece will decrease, the liquid retention capacity will continue to decrease, the ion conductivity will decrease, and the conductive network will deteriorate, thereby increasing the internal resistance of the battery, thereby affecting the cycle performance of the battery, and the high surface density will cause the insertion / extraction path of lithium ions in the electrode to be extended and the resistance to increase, thereby reducing the cycle performance of the battery. The pole piece that meets the limiting surface density range of the pole piece has a moderate porosity, and has good liquid retention and ion conductivity.

[0118] Optionally, the surface density of the pole piece is 18±1mg / cm 2 When the softness value of the electrode is 550mN, 650mN, 750mN, 850mN, 950mN, etc., there is no limit. The softness value is obtained by testing with a softness tester. The smaller the softness value, the softer the sample.

[0119] Optionally, the solid content of the active slurry is increased by 3% to 9% after adding the electrode material additive. Increasing the solid content of the active slurry can reduce the amount of solvent used, improve the stirring efficiency and coating efficiency, and the high-solid content slurry has better stability and is not easy to settle.

[0120] Optionally, the dissociation elongation of the polymer chain link may be 5%, 6%, 7%, 8%, 9%, 10%, etc., without limitation. The dissociation elongation is also related to the dissociation elongation of the polymer chain link when the active slurry is coated and dried and the first group of decomposition bodies is XX-XX. If the dissociation elongation of the polymer chain link is too low, it will result in a small proportion of the polymer chain link released and stretched into a chain structure, which will not be able to effectively disperse and has poor energy dissipation capacity, and the effect of improving the flexibility of the pole piece is poor. The proportion of the release and extension of the polymer chain link that meets the dissociation elongation range of the polymer chain link is large, which can greatly improve the flexibility of the pole piece, and will not cause obvious deterioration of the elongation rate of the pole piece under extreme compaction conditions.

[0121] Optionally, the pole piece peeling force may be 0.5N / cm, 0.55N / cm, 0.6N / cm, 0.65N / cm, 0.7N / cm, etc., without limitation. When the pole piece peeling force is too small, the active material layer is easily peeled off from the current collector, resulting in an increase in the internal resistance of the battery and a decrease in the capacity, thereby affecting the cycle performance of the battery. When the pole piece peeling force is too large, it may make it more difficult to separate the active material layer from the current collector during the pole piece preparation and battery assembly process, increasing the difficulty and cost of processing. The pole piece that meets this pole piece peeling force range has good battery cycle performance and processing stability.

[0122] Optionally, the elongation of the pole piece can be 1%, 0.8%, 0.6%, 0.4%, 0.2%, etc., without limitation. When the elongation of the pole piece is too high, it may cause uneven thickness distribution of the pole piece during rolling, thereby affecting the compaction density and electrochemical performance of the battery. And the pole piece with uneven thickness may produce uneven current distribution during the battery charging and discharging process, thereby affecting the performance and life of the battery. The pole piece that meets this elongation has a uniform thickness distribution during rolling, and the corresponding battery has good compaction density and electrochemical performance.

[0123] Optionally, the number of times the pole piece is folded can be 4, 5, 6, 7, 8, etc., without limitation. If the number of times the pole piece is folded is too small, the thickness of the pole piece and the distribution of active materials may be uneven, which may increase the internal resistance of the battery, generate more heat during the charging and discharging process, reduce the efficiency of the battery, and may shorten the life of the battery. The thickness of the pole piece and the distribution of active materials that meet this folding number range are uniform, and the battery efficiency is good.

[0124] The present invention provides a battery, comprising an electrolyte, a separator and a pole piece as described in any one of the above embodiments.

[0125] In one embodiment, the battery can be a composition system commonly used in the prior art, for example including a negative electrode plate, an electrolyte membrane and a positive electrode plate. The electrolyte can be a solid electrolyte or a liquid electrolyte. When a solid electrolyte is selected, the use of a diaphragm can be adaptively selected; both the positive electrode plate and the negative electrode plate can include the electrode material additives provided above.

[0126] The technical solution of the present application is described in detail below through specific embodiments.

[0127] Example 1

[0128] This embodiment provides an electrode material additive. The molecular structure of the electrode material additive can be referred to Figure 5 The electrode material additive includes a first component and a second component, wherein the first component includes a core and a shell, the shell is coated on the periphery of the core, the core includes a polymer segment (succinic anhydride double-terminated modified polydimethylsiloxane), the shell includes an end chain (polyether containing an amino anchoring group), the polymer segment and the end chain are connected by a chemical bond, and the polymer segment includes a silicon-oxygen bond. The second component is an adhesion promoter (polyacrylonitrile). Among them, the weight average molecular weight of the first component is about 1000, the weight average molecular weight of the second component is about 100000, the degree of polymerization of the polymer segment is 4 to 8, and the dispersibility of the first component is 1.8.

[0129] The preparation method of the electrode material additive provided in this embodiment is as follows:

[0130] 1) Add 1 part of succinic anhydride double-terminated modified polydimethylsiloxane and 0.05 parts of emulsifier into a flask containing 2.5 parts of deionized water, stir at 800 rpm and heat to 70°C under a protective airflow environment, add an appropriate amount of sodium bicarbonate to adjust the solution pH to 8.0, and continue to disperse for 1 hour to obtain O / W (oil in water) emulsion microspheres.

[0131] 2) Add a certain weight of polyetheramine D230 containing amino anchor groups (the molar ratio of succinic anhydride functional groups to single-terminal amino functional groups of succinic anhydride double-terminated modified polydimethylsiloxane is 1:1.2) and 0.02 parts of pyridine (added in 2 times) to the mixed emulsion of O / W (oil-in-water) emulsion microspheres, stir and react for 6 hours to obtain a low molecular weight polyether@polydimethylsiloxane emulsion containing amino anchor groups.

[0132] 3) Add 0.1 parts of calcium chloride to disperse and demulsify for 0.5 hours, filter, wash with pure water and ethanol for multiple times, filter, and dry (evaporate under reduced pressure at 70°C for 10 hours) to obtain a core-shell structured flexible and anti-cracking additive with polydimethylsiloxane as the core layer and a low molecular weight polyether containing an amino anchoring group as the shell layer.

[0133] 4) Mix and disperse the softening and crack-proofing agent, polyacrylonitrile (Mw-100000), and NMP in a weight ratio of 47.5:2.5:50 to obtain an electrode material additive containing 50% of the active component.

[0134] Example 2

[0135] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the terminal chain does not include an anchoring group, and the terminal chain is a polyether. In step 2) of the preparation method, D230 is changed to a monoamine-based polyetheramine.

[0136] Example 3

[0137] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the weight average molecular weight of the first component is about 500. In step 1) of the preparation method, the succinic anhydride di-terminated modified polydimethylsiloxane with a degree of polymerization of 4 to 8 of the polymerized chain segment is replaced with a succinic anhydride di-terminated modified dimethylsiloxane with a degree of polymerization of 2 to 3; in step 2), the polyetheramine D230 is replaced with ethanolamine.

[0138] Example 4

[0139] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the weight average molecular weight of the first component is about 4000. In step 2) of the preparation method, D230 is changed to a polyetheramine with a weight average molecular weight of 1700.

[0140] Example 5

[0141] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the degree of polymerization of the polymer segment is 1. In step 1) of the preparation method, the succinic anhydride di-terminated modified polydimethylsiloxane with a degree of polymerization of 4 to 8 of the polymer segment is replaced with a succinic anhydride di-terminated modified dimethylsiloxane with a degree of polymerization of 1. In step 2) of the preparation method, the polyetheramine D230 is changed to a polyetheramine with a weight average molecular weight of 400.

[0142] Example 6

[0143] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the selection of the end chain is adjusted. In step 2) of the preparation method, PEG200 (polyethylene glycol with a weight average molecular weight of 200) is used to replace polyetheramine D230.

[0144] Example 7

[0145] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the dispersibility of the first component is 10.5. In step 1) of the preparation method, succinic anhydride double-terminated modified polydimethylsiloxane with a polymerization degree of 1 to 10 is used to replace succinic anhydride double-terminated modified polydimethylsiloxane with a polymerization degree of 4 to 8.

[0146] Example 8

[0147] This embodiment provides an electrode material additive. The difference between this embodiment and embodiment 1 is that the polyetheramine containing an amino anchoring group in embodiment 1 is replaced by a polyether having an amino group at one end and a phenol at the other end.

[0148] Example 9

[0149] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that the degree of polymerization of the polymer chain segment is 37 to 45. In step 2) of the preparation method, the succinic anhydride di-terminated modified polydimethylsiloxane with a degree of polymerization of 4 to 8 of the polymer chain segment is replaced with a succinic anhydride di-terminated modified polydimethylsiloxane with a degree of polymerization of 37 to 45.

[0150] Example 10

[0151] This embodiment provides an electrode material additive, and the difference between this embodiment and embodiment 1 is that there is no second component. In step 4) of the preparation method, succinic anhydride double-terminated modified polydimethylsiloxane with a polymerization degree of 4 to 8 is directly mixed and dispersed with NMP in a weight ratio of 1:1 to obtain an electrode material additive containing 50% of the active component.

[0152] Comparative Example 1

[0153] This comparative example provides an electrode material additive, namely polydimethylsiloxane with a degree of polymerization of 4 to 8.

[0154] Comparative Example 2

[0155] This comparative example provides an electrode material additive. The difference between this comparative example and Example 1 is that the polymer segment of this comparative example is polyvinyl alcohol (weight average molecular weight is 100000).

[0156] Comparative Example 3

[0157] This comparative example provides a battery. The difference between this comparative example and Example 1 is that this comparative example does not have an electrode material additive.

[0158] The dispersant parameters provided by Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1:

[0159] Table 1 Electrode material additive parameters provided in Examples and Comparative Examples

[0160]

[0161]

[0162] A method for preparing a lithium ion battery comprises the following steps:

[0163] 1) Preparation of positive electrode sheet: 96.5g lithium iron phosphate DY-12, 1.3g Super P, 2.2g positive electrode binder, 0.2g electrode material additive (the amount of electrode material additive added is 0.2% (mass fraction) of the main active material) and XXg NMP (adjusted according to the solid content of the slurry) are mixed, and the positive electrode slurry is dispersed by a degassing machine, the dispersion time is 30min, the rotation speed is 2000rpm, the positive electrode slurry is coated on the opposite sides of the aluminum foil, and after rolling, it is vacuum dried at 120°C overnight to obtain a positive electrode sheet. Among them, the positive electrode binder is the dispersant of each embodiment or comparative example.

[0164] 2) Preparation of negative electrode sheet: 95g of graphite, 2g of Super P, 0.5g of carboxymethyl cellulose, and 2.5g of styrene-butadiene rubber (SBR) were placed in deionized water and mixed evenly to prepare negative electrode slurry, and the negative electrode slurry was coated on the opposite sides of the copper foil. After drying-rolling-secondary drying process, the negative electrode sheet was obtained.

[0165] 3) Preparation of electrolyte: Ethylene carbonate (EC) and ethyl methyl carbonate (DEC) were mixed in a volume ratio of 3:7, and LiPF6 was added to form an electrolyte, and the concentration of LiPF6 was 1 mol / L.

[0166] 4) Battery (lithium-ion battery) assembly: A lithium-ion battery is assembled in an argon inert atmosphere glove box in the order of negative electrode sheet - separator - electrolyte - positive electrode sheet.

[0167] The materials and products provided in the above Examples 1-8 and the materials and products provided in Comparative Examples 1-3 were tested as follows. The test results are shown in Tables 2 and 3:

[0168] 1. Test of the softness of the positive electrode: GB / T 8942 "Determination of paper softness" is used to test the positive electrode. The test principle is that under specified conditions, when the plate probe presses the sample into the slit to a certain depth (20mm), the instrument records the bending resistance of the sample itself and the maximum vector sum of the friction between the sample and the slit, which is called the softness of the sample. The smaller the instrument reading, the softer the sample. The surface density of the positive electrode is set at 18mg / cm 2 .

[0169] 2. Test of the limiting surface density of the positive electrode: The slurry is coated according to different coating scales. According to the maximum mass of the coated positive electrode without cracking, repeat the test for 3 groups, take the average value, and then perform surface density conversion to obtain the maximum surface density value.

[0170] 3. Folding test method of the electrode: Fold the electrode in half and use a 2Kg roller to roll it back and forth 3 times, then flatten the electrode and repeat the above operation (folding forward and backward) until light leaks from the folded part, and record the number of folds. Test each group 5 times and take the average value.

[0171] 4. Lithium-ion battery performance test: Observe the first cycle charge and discharge capacity of the battery at 0.1C at room temperature (25±3℃).

[0172] 5. Test of lithium-ion battery cycle stability: In a room temperature (25±3℃) environment, cycle 400 times at 1C rate and observe the change in battery capacity.

[0173] 6. Lithium-ion battery peeling force test: At room temperature (25±3℃), fix the width and length of the electrode, use a certain specification of tape, and use a tensile testing machine to test the peeling strength of the electrode.

[0174] Table 2 Test results of positive electrode sheets corresponding to various embodiments and comparative examples

[0175]

[0176] With reference to Table 2, it can be seen from the test results of Examples 1-8 and Comparative Examples 1-3 that the average slurry solid content of the electrode material corresponding to the electrode material additive provided in the present application is greater than that of the comparative example, and the folding flexibility, average ultimate compaction density, and average peel strength of the electrode sheet corresponding to the electrode material additive provided in the present application are all greater than those of the comparative example, indicating that the energy density of the electrode material containing the embodiments of the present application is higher, the stability of the slurry is better, the softness of the electrode sheet containing the embodiments of the present application is better, and the material distribution on the electrode sheet is more uniform. Fig. 9 a in the figure is the pole piece corresponding to Example 1, Fig. 9 b in the figure is the pole piece corresponding to comparative example 3. Fig. 9 It can be seen that Fig. 9 After the electrode in a is folded 8 times, there is no crack on the electrode and it is not transparent. Fig. 9 After the electrode in b was folded five times, obvious cracks appeared on the electrode and the electrode was obviously transparent, indicating that the folding flexibility of the electrode in Example 1 was significantly better than that of the corresponding electrode in Comparative Example 3. Fig.10 a in the figure is the result of thick coating of the electrode corresponding to Example 1. Fig. 9 b in the figure is the result of thick coating of the electrode corresponding to comparative example 3, where: Fig.10 The average surface density of the pole piece in a is 55.8 mg / cm 2 , Fig.10 The average surface density of the electrode in b is 36.1 mg / cm 2 , and by Fig.10 It can be seen that Fig.10 The electrode in b has multiple cracks and the cracks are obvious. Fig.10 There is no cracking on the pole piece in a, indicating that the average surface density and pole piece flexibility of the pole piece of Example 1 are better than those of the pole piece of Comparative Example 3.

[0177] It can be seen from the test results of Example 1 and Example 2 that the first component with an anchoring group in the end chain can, as a softening and anti-cracking agent, to a certain extent provide better solid content of the slurry. The pole piece has a lower elongation at the limiting surface density and a greater peel strength, but the performance is still better than that of Comparative Example 1.

[0178] It can be seen from the test results of Example 1, Example 3 and Example 4 that after changing the weight average molecular weight of the first component, the limiting surface density, limiting compaction density, peel strength and folding flexibility of the pole piece change; the weight average molecular weight of the first component of Example 3 is too small, which will cause the first component to be unable to provide sufficient flexibility for the pole piece, affecting the durability of the battery; the weight average molecular weight of the first component of Example 4 is too large, which will cause the corresponding slurry of Example 4 to have too high solid content, thereby making the fluidity of the slurry poor and difficult to coat evenly; but compared with Comparative Example 1, the performance is still better. The weight average molecular weight of the first component of Example 1 is moderate, and the corresponding electrode slurry has good fluidity during electrode coating, which is convenient for coating the pole piece, so the limiting surface density, limiting compaction density and peel strength of the pole piece are greater, and the folding flexibility of the pole piece is better.

[0179] It can be seen from the test results of Example 1 and Example 5 that after changing the degree of polymerization of the polymer chain link of the first component, the ultimate surface density, ultimate compaction density, peel strength and folding flexibility of the pole piece change; the degree of polymerization of the first component of Example 5 is too small, which will cause the molecular chain of the polymer chain link to be shorter, thereby causing the first component to be difficult to rotate and have poor intrinsic flexibility, and the corresponding pole piece has poor folding flexibility; but compared with Comparative Example 1, the performance is still better; the degree of polymerization of the first component of Example 1 is moderate, the intrinsic flexibility of the first component is good, the corresponding pole piece has better folding flexibility, and the ultimate surface density, ultimate compaction density and peel strength of the pole piece are also better.

[0180] It can be seen from the test results of Example 1 and Example 6 that only by changing the type of the end chain of the first component, the solid content and compatibility of the slurry remain basically unchanged, and the corresponding electrode pieces' folding flexibility, ultimate surface density, ultimate compaction density and peel strength are also similar, and the electrode pieces still have good flexibility.

[0181] It can be seen from the test results of Example 1 and Example 7 that after changing the dispersibility of the first component, the solid content of the electrode material slurry and the limiting surface density, limiting compaction density and peel strength of the pole piece change; the polydispersity of the molecular weight of the first component of Example 5 is too high, which will make the low molecular weight part of the first component easily become a stress concentration point, causing the first component to be more likely to break when subjected to force; but compared with Comparative Example 1, the performance is still better. The polydispersity of the molecular weight of the first component of Example 1 is moderate, and the first component is not easy to break when subjected to force, so that the folding flexibility of the pole piece corresponding to Example 1 is better.

[0182] It can be seen from the test results of Example 1 and Example 8 that only by changing the type of anchoring group of the first component, the solid content and compatibility of the slurry remain basically unchanged, and the corresponding electrode's folding flexibility, ultimate surface density, ultimate compaction density and peel strength are also similar, and the electrode still has good flexibility.

[0183] It can be seen from the test results of Example 1 and Example 9 that the solid content of the slurry and the limiting surface density, folding flexibility, limiting compaction density and peel strength of the pole piece change by changing the degree of polymerization of the polymer chain segment of the first component. The degree of polymerization of the polymer chain segment will affect the molecular size of the first component, thereby affecting the distribution of the first component in the slurry and the viscosity of the slurry. Therefore, it is necessary to control the degree of polymerization of the polymer chain segment of the first component in an appropriate range, and it cannot be too large or too small. However, compared with the first component with a linear chain structure in Comparative Example 1, the limiting surface density, elongation at the limiting surface density and peel strength corresponding to the pole piece of Example 9 are better than those of Comparative Example 1.

[0184] It can be seen from the test results of Example 1 and Example 10 that the addition of the second component as an adhesion additive changes the solid content of the slurry and the limiting surface density, folding flexibility, limiting compaction density and peel strength of the pole piece. The adhesion additive can improve the adhesion between materials and improve the dispersion of particles in the battery material, so it is necessary to control the addition of the second component. However, compared with the first component of the linear structure in Comparative Example 1, the corresponding folding flexibility, limiting surface density, elongation at limiting surface density and peel strength of the pole piece of Example 10 are better than those of Comparative Example 1.

[0185] It can be seen from the test results of Example 1 and Comparative Example 1 that compared with the first component of the linear structure, the first group of the core-shell structure has better compatibility with the slurry system due to the wrapping of the polar shell, and the peel strength, folding flexibility and elongation of the electrode at the limiting surface density are significantly improved. Therefore, the corresponding folding flexibility of the electrode is also better, that is, the flexibility of the electrode is better; at the same time, although Comparative Examples 2 and Comparative Examples 3 can also achieve the level of a small number of cracks, their surface densities are relatively small and they cannot meet better performance requirements.

[0186] Table 3 Test results of lithium-ion batteries corresponding to various embodiments and comparative examples

[0187]

[0188] As shown in Table 3, the test results of Examples 1-10 and Comparative Example 1 show that the battery using the first component with a core-shell structure as a flexible and anti-cracking agent has better performance than the battery using the first component with a straight-chain structure as a flexible and anti-cracking agent. As shown in Examples 1-10, the first component corresponding to Examples 1-10 does not substantially affect the electrochemical performance of the battery as a flexible and anti-cracking agent. In addition, the electrode is overall stable during the cycle, and the electronic and ion network pathways are smooth, so it is also possible to maintain a higher initial coulomb efficiency and cycle retention rate.

[0189] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship described in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0190] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiment and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. An electrode material additive, characterized in that: It comprises an end chain and a polymer chain segment containing a silicon-oxygen bond, wherein the end chain is connected to the end of the polymer chain segment, and the end chain comprises a polar segment; the polymer chain segment is spun together to form a core body, and the end chain forms an outer shell to cover the core body.

2. The electrode material additive according to claim 1, characterized in that: The molecular formula of the terminal chain and the polymeric chain segment containing silicon oxygen bonds comprises R q -(C2H6SiO) n SiC2H6-R q , where R q For the terminal chain, (C2H6SiO) n is the polymer chain segment.

3. The electrode material additive according to claim 2, characterized in that: R q Including R α (R β ) p R γ , where R α Including anchoring groups, R β Including polar segments, R γ It comprises a connecting group segment, wherein the connecting group segment connects the polar segment and the polymer segment, wherein 2≤p≤20.

4. The electrode material additive according to claim 3, characterized in that: The anchoring group includes at least one of an ether bond, a carbonyl group, an ester group, an amide group, a hydroxyl group, a carboxylic acid group, a phosphoric acid group, a phenol, an amine group, a benzene ring, a sulfonic acid group, a phosphate ester group, and a hydrazine; and / or The polar segment includes at least one of a polyester segment, a polyether segment, and a polyacrylate segment.

5. The electrode material additive according to claim 1, characterized in that: The weight average molecular weight of the terminal chain and the polymeric chain segment containing silicon-oxygen bonds is 700 to 3500; and / or The degree of polymerization of the polymerized chain segment is 4 to 30; and / or The molecular weight dispersity of the terminal chain and the polymer chain segment containing silicon-oxygen bonds is 1.2-3.

6. The electrode material additive according to claim 1, characterized in that: The electrode material additive further includes an adhesion additive, and the adhesion additive includes at least one of polyacrylonitrile, polyvinyl alcohol, polyacrylic acid, polyvinylidene chloride, polyimide, polyamide, and polyethyleneimine.

7. A method for preparing an electrode material additive, characterized in that: include: The first precursor and the second precursor are mixed and reacted according to a mass ratio to obtain an electrode material additive; Among them, the first precursor contains a polymer chain segment containing a silicon-oxygen bond, and the second precursor contains an end chain, and the end chain includes a polar segment; the end chain is connected to the end of the polymer chain segment, the polymer chain segment is rotated into a core body, and the end chain forms an outer shell to cover the core body.

8. The method for preparing an electrode material additive according to claim 7, characterized in that: The first precursor and the second precursor are mixed and reacted according to a mass ratio, comprising: The first precursor and the first auxiliary agent are mixed and reacted according to a mass ratio to obtain a first solution; The second precursor and the second auxiliary agent are added to the first solution according to a mass ratio for mixed reaction to obtain the electrode material additive.

9. A battery comprising an electrolyte, a separator and a pole piece, wherein the pole piece comprises a current collector and an active material layer disposed on the current collector, characterized in that: The active material layer is formed by coating an active slurry, wherein the active slurry includes the electrode material additive according to any one of claims 1 to 6 or the electrode material additive prepared by the preparation method according to claim 7 or 8.

10. The battery according to claim 9, characterized in that The mass ratio of the electrode material additive to the active slurry is 0.05% to 0.3%; and / or The limiting surface density of the pole piece is 25 mg / cm 2 ~75mg / cm 2 ; and / or The ultimate compaction density of the pole piece is 2.68mg / cm 3 ~2.73mg / cm 3 ; and / or The surface density of the pole piece is 18±1 mg / cm 2 When the softness value of the electrode is 550mN to 950mN; and / or The surface density of the pole piece is 18±1 mg / cm 2 And the compacted density is 2.65±0.35mg / cm 3 When the pole piece is folded in half for 4 or more times; and / or When the active slurry is coated and dried and the shell and the core are disintegrated, the dissociation extension of the polymer chain segment is 5% to 10%; and / or The peeling force of the pole piece is 0.5N / cm to 0.7N / cm; and / or, The surface density and compaction density of the pole piece are 18±1 mg / cm 2 and 2.65±0.35mg / cm 3 When the pole piece has an elongation of ≤1.0%.

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